Electrical Engineering - Slow down a fan speed.

Author

Slow down a fan speed.

Mike Coonrod

2006-01-25, 9:21 pm

Electrial experts,
I have a hot dawg heater and would like to slow down the very powerful
fan that clicks on after the burn chamber gets hot, it is too loud in my
garage, drowns' out the football game. I looked at the heater itself
and I can NOT select any other options on the control board to set the
speed. Also, the fan on the back of the heater that I want to slow down
has a start capaciter, and I don't know is that is important but it may
be. Can I just look at the amp rating on the fan and add a reostat in
line with the feed to the motor? (I took two years of electronic backin
the 80's but don't use in day in and day out)

I have a call into Modine, the makers of the heater, but they do not
seem that user friendly. Thanks in advance.

Mike in cold Minnesota.

Pop

2006-01-26, 12:21 pm

There are ways to control inductive motor speeds, but
unfortunately a resistive solution isn't one of them. As you
decrease the current to a motor, the current increases sometimes
to the point of catastrophy. More likely the temp would rise
until an internal winding temperature sensor shuts the fan down.
Sometimes they are self resetting, sometimes not.
Check into motor controllers for a better solution.
Pop
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..
"Mike Coonrod" <mwc@umn.edu> wrote in message
news:dr97cd$58h$1@lenny.tc.umn.edu...
: Electrial experts,
: I have a hot dawg heater and would like to slow down the very
powerful
: fan that clicks on after the burn chamber gets hot, it is too
loud in my
: garage, drowns' out the football game. I looked at the heater
itself
: and I can NOT select any other options on the control board to
set the
: speed. Also, the fan on the back of the heater that I want to
slow down
: has a start capaciter, and I don't know is that is important
but it may
: be. Can I just look at the amp rating on the fan and add a
reostat in
: line with the feed to the motor? (I took two years of
electronic backin
: the 80's but don't use in day in and day out)
:
: I have a call into Modine, the makers of the heater, but they
do not
: seem that user friendly. Thanks in advance.
:
: Mike in cold Minnesota.
:

sQuick

2006-01-26, 3:21 pm

"Mike Coonrod" <mwc@umn.edu> wrote in message
news:dr97cd$58h$1@lenny.tc.umn.edu...
> Electrial experts,
> I have a hot dawg heater and would like to slow down the very powerful fan
> that clicks on after the burn chamber gets hot, it is too loud in my
> garage, drowns' out the football game. I looked at the heater itself and
> I can NOT select any other options on the control board to set the speed.
> Also, the fan on the back of the heater that I want to slow down has a
> start capaciter, and I don't know is that is important but it may be. Can
> I just look at the amp rating on the fan and add a reostat in line with
> the feed to the motor? (I took two years of electronic backin the 80's
> but don't use in day in and day out)
>
> I have a call into Modine, the makers of the heater, but they do not seem
> that user friendly. Thanks in advance.
>
> Mike in cold Minnesota.
>

I wouldn't recommend slowing it down. The fan was designed to run at
that speed for a reason.

Maybe look at replacing the fan with a quieter one of the same speed.

sQuick..

spamTHISbrp@yahoo.com

2006-01-26, 3:21 pm

Is the fan noise coming more from the front, or the back?

I'm thinking absorbing the noise is going to be more fruitful than
trying to make the heater generate less noise.

If you slow the fan down, or replace it with one that flows less air
(volume/time) the heater will likely overheat.

Can you post a link to what this critter looks like?

Dave

operator jay

2006-01-26, 8:21 pm

"sQuick" <squickdrill@hotmail.com> wrote in message
news:1138300467.21182.0@dyke.uk.clara.net...
>
> "Mike Coonrod" <mwc@umn.edu> wrote in message
> news:dr97cd$58h$1@lenny.tc.umn.edu...
fan[color=darkred]
and[color=darkred]
speed.[color=darkred]
Can[color=darkred]
seem[color=darkred]
>
> I wouldn't recommend slowing it down. The fan was designed to run at
> that speed for a reason.

I agree, and to elaborate for the OP, slowing down the fan may allow the
unit to overheat.

>
> Maybe look at replacing the fan with a quieter one of the same speed.
>
> sQuick..
>
>

Bud--

2006-01-27, 2:21 pm

operator jay wrote:

> "sQuick" <squickdrill@hotmail.com> wrote in message
> news:1138300467.21182.0@dyke.uk.clara.net...
>
>
> fan
>
>
> and
>
>
> speed.
>
>
> Can
>
>
> seem
>
>
>
> I agree, and to elaborate for the OP, slowing down the fan may allow the
> unit to overheat.
>
If it is gas fired yes.

Old Modine units were a hot water/steam radiator with fan forced air
through it. If it is one of these reducing the air flow shouldn't be a
problem.

Noise, air flow and power consumed fall off rapidly with lower speed,
What I remember is square law for air flow and power vs. RPM.

Do you get a lot more heat than you need - you will loose capacity fast
with lower speed.

Lower speed motor (which can be lower power).
Dual speed motor.
Different fan blade.

bud--
>
>
>
>

spamTHISbrp@yahoo.com

2006-01-27, 3:21 pm

But unless the OP comes back, it'll be another of those unsolved
mysteries.

I took "hot dawg heater" to mean one of those propane 'jet engine'
lookin' things.

D

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